Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/1998
Publication Date: N/A
Interpretive Summary: Respiratory tract diseases are a leading cause of loss from disease in the cattle, sheep and goat industries. Annual loss in the United States is estimated to exceed one billion dollars. Losses are from mortality, reduced feed efficiency, and slaughter condemnations, as well as prevention and treatment measures. Currently, not all the factors leading to the development of pneumonia are known by scientists and veterinarians. As part of our ongoing studies to understand the disease process, we found that the respiratory tract contains a number of natural antibiotics. In this study, we were able to show that these natural antibiotics are found in both respiratory tract secretions and upper respiratory tract lining cells but not in lower lung cells. This information will provide the background for prospective clinical studies of the role of these natural antibiotics in the etiology and treatment of respiratory infections in cattle, sheep and goats. Our findings are an important first step in the development of a new treatment that can be used to better control shipping fever of cattle. Corollary benefits include an increase in the profitability and international competitiveness of the U. S. cattle industry, a stronger rural economy, and a continued supply of inexpensive, wholesome beef, and beef products for the American consumer.
Technical Abstract: Surfactant-associated anionic peptides (SAAP), three antimicrobial peptides (721.6 to 823.8 Da), were originally isolated from ovine pulmonary surfactant preparations. However, their presence in other secretions and tissues of the respiratory tract is unknown. To assess this, an affinity purified rabbit antibody and a monoclonal antibody to H-DDDDDDD-OH were prepared. SAAP was found in ovine bronchoalveolar lavage (BAL) fluid of 2 sheep by RP-HPLC and by ELISA (0.86 mM + 0.26 mM SD, range 0.46 to 1.25 mM). In western blots of respiratory tract tissue, both antiserums recognized 3 bands in solubilized turbinate and tracheal epithelial cell scrapings (31.2, 28.0, and 25.7 kDa) and 5 bands in lung homogenates (53.5, 37.1, 32.2, 28.0, 25.7 kDa). A single band was seen in liver and small intestine homogenates whereas no bands were seen in ovine serum albumin or kidney and spleen homogenates. Immunocytochemical staining of respiratory tissues was specific for the apical cytoplasm of the bronchial and bronchiolar epithelium and the cytoplasm of pulmonary endothelial cells and an occasional alveolar macrophage. Goblet cells and epithelial cells of pulmonary alveoli were not stained. The nuclei of some bronchial and bronchiolar epithelia were brightly stained whereas the nuclei of other cell types (e.g. cells from submucosal glands of bronchi, serous cells, endothelial cells, smooth muscle cells alveolar macrophages, and alveolar septal cells) varied in intensity and number. The significance of this is not yet known. SAAP in both respiratory secretions and respiratory epithelium would provide an antimicrobial barrier refractory to microbial infection and colonization.